The aim of the proposed study is to identify and characterize spinal reflexes in the normal adult male rat that are associated with sexual behavior and to examine the effects of sex hormones on these reflexes. One output pathway which has been identified in the rat is the spinal nucleus of the bulbocavernosus (SNB). These motoneurons, which innervate the levator ani and the bulbocavernosus muscles, are known to bind exogenous androgens and to be sensitive to androgens during development and adulthood. Therefore, spinal reflexes involving SNB motoneurons may serve as an excellent model for studying the effects of sex steroids on the mammalian CNS. The effects of hormone deprivation (castration) with and without hormone substitution (testosterone, 5 Alpha-dihydrotestosterone and 17 Beta-estradiol) on SNB motoneurons will be examined. In vivo intracellular recording techniques will be used to investigate the membrane properties and firing characteristics of SNB motoneurons as well as synaptic potentials elicited by electrical stimulation of perineal afferents. In addition, the anatomy of these motoneurons will be studied using retrograde labeling with wheat germ agglutinin (WGA) and intracellular injection of horseradish peroxidase (HRP) with subsequent reconstruction at the light microscopic level. The long term objectives are to use these spinal reflexes as a model system in which to study the action of sex steroids, and elucidate their mechanisms of action during development and adulthood.